Glazing and polishing machine



Sept. 30, 1952 w, c, BURT 2,612,005

GLAZING AND POLISHING MACHINE 2 SHEETS--SHEET 1 Filed March l, 1950 70 Z 'l/zo 92 /241' "7b Q@ 9b W. C. BURT GLAZING AND POLISHING MACHINE Sept,i 30, 1952 Filed March l l 1950 2 Sl'lEETS-Sl-IEET 2 Patented Sept. 30, 1952 'i'ED omai-No AND romsnnvo MACHINE William C. Burt, Olean, N. Y., assigner to Clair Manufacturing Company, Inc., Olean, N. Y.

Application March 1, 195), Serial No. 147,053

8 Claims. 1

rlhis invention relates to improvements in surface nishing machines of the typeknown as glazing and polishing machines, and more particularly to machines for glazing and polishing multiple lots of cutlery articles, tools, hardware, and the like. Furthermore, the present invention relates to improvements in the general type of machines disclosed in United States Patents Nos. 2,188,223, 2,269,311, and 2,458,708, and embodies improvements in the art thereover whereby such machines may be more versatile and more fully automatic in their operation.

One of the objects of the present invention is to provide an improved machine for polishing and glazinor articles, as aforesaid. Another object of the invention is to provide in a machine for the purposes aforesaid, improved automatic means for stopping and opening the machine subsequent to a preselected time cycle of operation, for unloading and reloading of the machine. Another object ofthe invention is to provide an improved machine for the purposes aforesaid, embodying improved work piece mount positioning and stroke control relative to the glazing or polishing rolls whereby thework pieces are fed to the polishing or glazing rolls in improved manner. Another object of the invention is to provide an improved machine for the purposes aforesaid, embodying improved work piece movement control features, whereby the workpieces are automatically motivated relative to the machine rolls during each operative cycle inimproved manner. Other objects-and advantages of the invention will appear in the specification hereinafter.

In the drawings:

Fig. 1 isa fragmentary top plan view of the front end portion of a polishing or glazing machine constructed in accordance with the invention;

Fig. 2 is a front elevational view thereof;

Fig. 3 is a fragmentary end view with portions shown in section taken along line III- III of Fis. 2;

Fig. 4 is a fragmentary sectional detail taken along line IV-IV of Fig. 2;

Fig. 5 is a fragmentary section taken along line V-V of Fig.' 2;

Fig. 6 is a `fragmentary section taken along n line VI--VI of Fig. l;

Fig. 7 is a schematic diagramof aportion of the pneumatic-hydraulic automatic cycling and workpiece feeding reciprocation control mechanism of the machine;

Fig. 8 is a diagram of a portion of the hydraulic workpiece oscillation control mechanism; and

Fig. 9 is a diagram similar to Fig. 8 of another portion of the workpiece oscillation control mechanism.

The drawing illustrates the invention asA being employed in conjunction with a machine such as is shown in thePatents Nos. 2,188,223 and 2,458,708 referred to hereinabove. That is, the present invention embodies an operative mechanism which is mounted upon the4 basic machine as disclosed in theraforesald patents as an accessory thereto so as to embody in the latter improved automatic control means forthe purposes aforesaid. As illustrated in Figs; 1, 2, 3 for example, the basic machine includes a base or frame I0 supported by legs I2 to a convenient height; frame I0 in turn supporting the oscillating work piece carriage and the polishing vor glazing rolls, and other mechanisms for driving and controlling the carriage and the rolls aswill be explained hereinafter.

.The rolls are indicated at lei-I6; the roll I4 being mounted above the roll I6 and with its axis of rotationset slightly ahead of the axis of the roll I. The roll I4 is of substantially Vless diameter than the roll I6, and the rolls are a1'- ranged to contact along the line of entering of the ware to'be polished or glazed. vThe rolls i-I will ofcourse be formed of any suitable material treatedin any desired .manner according to the character of the work to be done, and the roll I4 is carried upon a shaft i8`while the roll it is carried upon a shaft I9.

The shaft I8 is journaled at its opposite ends upon rocker arms 20 which extend from opposite ends of a common rocker shaft 24; the shaft 26 being in turn rotatably supported by means of pedestals 28 which extend vertically from opposite ends of the base plate I0. A second rocker shaft 30 is similarly journaled upon the pedestals 23 so as to extend parallel to the rocker shaft 255 and therebelow. Rocker arms 32 extend forwardly from opposite ends of the rocker shaft 3i! in parallel relation and-carry at their outer ends the lower roll shaft I9 in journaled .relation thereon. The rocker shafts 24, 30 are interconnected by means of meshing gears 36, 38lwhich` are keyed to the rocker shafts 24, 3l), respectively. Adjacent the opposite ends'of'ithe `rolgsker shafts 2li, 3i! they'are tted with rearwardly xtending clevis arms 40, 42. Thearm 40 vcarries a screw block 44 pivotally mounted thereinand the arm 52 carries a vertically splined stirrup i8 thereon. A hydraulic cylinder member 48-is fixed to the vlower end of the ystirr'up'lli:` and slidably mounts therein a pistonBtLQ The piston' is xed upon the lower end of a -screw52` which ,extends upwardly through the open end of the cylinder 48 and thence through the clevis end portion of the crank arm 42 and thence through the nut 44 which it engages in screwthreaded relation. At its upper end the screw 52 carries a hand wheel 55. A tension spring device 58 is connected at its upper end to the screw block 44 and at its lower end upon a hook device 59 which is fixed to the slide bracket 46. Thus, it will be appreciated that the spring 58 tends to bias the crank arms 40, 42 so as to open the rolls:

III-I6, but that the piston cylinder unit 48, 50 is operable to force the rocker cranks apart so as to bring the rolls I4, I6 together for. polishing work pieces inserted therebetween; Also, it will be appreciated that the hand wheel 56 is manually adjustable for purposes of regulating theA tension and distance between the rolls under operating conditions, so as to suit the machine to different classes of work. The rolls I4, I6 are arranged to be driven by any suitable means such as separate electric motors as shown and describedfor' example in Patent No. 2,458,708.

The work mounting carriage portion of the machine is illustrated herein to comprise a table 'I0 which is mounted upon. the base plate I0 by means ofv slideways 'I2 so that the table 'I0 is reciprocable horizontally in directions transverse to the rolls I4, I6. A hydraulic piston-cylinder unit'15v is mounted under the base plate I0, and the piston rod 'IGthereof extends in thedirection of platform. travel. and into connection with a bracket 'I'I carried by the platform 10. Thus, hydraulic actuationl of the piston-cylinder unit I5 will cause the platform; I0A to reciprocate toward and away from the rolls I4, I6.

A second platform 80 carrying an' elevated rail 8| is mounted by means' of rollers 82 (Fig. 2) which are. carried by an upright extension of the platforml' so that the platform 80 is reciprocable relative to the platform I in directions axially of the rolls I4, I6 independently of reciprocation of the platform 70. A hydraulic pistoncylinder unit 83 is mounted upon the platform l0, and the piston rod 84 thereof is connected at 85 tothe platform 80, whereby hydraulic actuation of the piston cylinder unit 83 will cause the platform 80to reciprocate iny sidewise directions independently of backward and forward reciprocations of the platform '|0.

The platform structure 80-8I includes upright 86-86 (Fig. 2) and on lone end a side plate 81 which is bolted thereto by bolts 88, 88. The uprights 85, 86 mount top rails 90, 00 which extend forwardly of the brackets 86 and mount in journaled relation thereon a rocker shaft 92 which extends parallel to the rolls I4, I6. At one end ofthe rocker shaft 92 it carries a quadrant 94 which in turn mounts a crank pin 96. The piston rod 98 of a hydraulic cylinder-piston unit |100 is connected to the crank pin 96; the closed endv of the'cylin'der |00 being pivotally mounted upon thebracket plate 81 as by means of a pin |0I (Fig. 3). The quadrant 04 is arcuately slotted as indicated at |02 concentrically of its mounting shaft B2, 4and a, trip pin |04 is adjustably disposed in the slotted portion I02. A second trip pin |06 is also disposed in the groove I 02 adjacent the lower end thereof, and the pins |04, |08` are positionallyadjusted on the quadrant 94 so that as the4 quadrant oscillates in response to an operation which Will bek explained hereinafter, the pins |04; |08 alternatelycontact the actuatingv arm |08 of a four-way hydraulic pilot control valve IIO,. for actuating the latter.

The arms 90, 80 also mount short rocker shafts I|2|I2- (Fig. 3) and the rocker shafts |I2 are connected to the cross shaft 92 by means of meshing gears H4, IIB enclosed within gear cases Hl. Each rocker shaft I2 carries a bracket IIB, and thus it will be appreciated that whenever the hydraulic piston cylinder unit |00 operates to reciprocate.4 the quadrant 84, lthe rocker shaft and gear mechanism will operate to simultaneously cause the brackets IIS-IIB to rock upon the shafts II-2-I I2.

The brackets I I8-I I8 are grooved as indicated at |720 to receive` in slide-fitting relation therein the-oppositefpin-shaped ends |23 of a work carrying. plate |24, so that the latter may be slipped through the grooves |20 until the pin ends |23 run into the bottom ends of the grooves. Thus, a gang. of spoons or forks or the like as indicated at |25 may be clamped upon the plate |24, as by means. of a detachable holder bar |26, so that the work pieces are mounted to extend therefrom toward the builing'rolls. TheA rolls I4, I8 rotate in such direction as toat` all times tend to draw the work pieces into the polishingA gap.

Thev quadrant 94 and the brackets IIB-IIS and' the operating. mechanisms therefor are so constructed and arranged as to cause the work piece holdingmembers to swing about the axes of the shaftsA II2-I I2, incidental to which the work pieces are causedto oscillate. Thus, it will be understood that the. curved or bowl portions of the work pieces will bethereby caused to pass in and. out between. the rolls so as to provide progressive polishing or glazing of the curved bowl portions from the'tip ends to the heel ends thereof; and that; the movements of the brackets I I8- H8' and the pivotingv of the work holder plate thereon permits the curved surfaces of the work piecesto move in intimateA polishing contact with the rolls throughout all phases of displacement.

The control system for the mechanism is illustrated in Figi. 7 to include a start-stop switch 208 in series with an emergency switch 202, a counter swit'ch203, and the winding of a solenoid 204; in a circuit comprisingl conductors 205-206 connecting to any suitable power source. The emergency and counter switches are normally closed and therefore closingA of switch 200 energizes the solenoid to operate a four way pneumatic valve 2.08 so as to permit air to flow under pressure from conduit 209. through conduit 2|0 and conduit 2 I I into the pneumatic jack 48 so as to close the rolls I4, and I6'. At the same time air passing through conduit 2 I0 enters an air-controlled hydraulic valve 2|2 so as to actuate the shuttle thereof. topermit pressured uid. to ow from a pump.2 I4 through a conduit 2I5 and into a conduit 2 I6 leading into the pressure supply port of a four way hydraulic valve 220. The return air lines are indicated at. 22I-222, and the return hydraulic lines are. indicated at 223-2 24. A pressure relief valve is indicated at 225 for protecticn.. of the systems.

The valve 220 is of the shuttle type and is shown toinclude paired output ports coupled to conduits 22E-221 which connectv to opposite ends of the cylinder 'I5 to produce the in-and-out motion of the work carriage; and the valve 220 is controlled to produce reciprocation of the carriage by means of a carriage-tripped pilot valve 230 which is connected by conduits 23|, 232, 233, 234 to the hydraulic pressure supply and return conduitsandto the shuttle control ports of the valve 220.

As shown in Fig, 8, the control for sidewise reciprocation of the work carriage is eifected by a mechanism includingI a shuttle valve 235 which is similar to valve 22D, and a carriage-tripped pilot valve 236 (Figs. 1-2) which is similar to valve 230; the valves 235-236 being connected to control the carriage operating cylinder 83 by means of suitable conduits as shown which correspond to the conduit connections and control arrangement referredto in Fig. 7.

As shown in Fig. 9, the control for the cylinder H30 which produces rocking of the work piece holding carriage H8 is effected by means of a hydraulic control mechanism includinga shuttle valve 240 and the sector-tripped pilot valve IIB (Fig. 3) both of which are of a type similar to that of the trip valves 23E- 236. The valves SiO- 240 are connected to control the operation of the cylinder |00 by means of suitable conduits asshown which correspond to similar conduits shown in Figs. 7 8.

Thus, it will be appreciated that the control mechanism will operate upon closing of the starting switch 260 to first close the rolls i4, l5, and then to cause the carriage to reciprocate toward the rolls and transversely thereof while at the same time the work piece carrying platform H8 is caused to rock about the axis of the shaft H2, thereby effecting proper glazing or polishing of the work pieces. However, it is to be understood that the invention is not limited to the use 'of the three specific oscillation motions of the work pieces referred to hereinabove; and that one or more of such motions might be eliminated if not needed in the case of any given glazing or polishing problem. Upon completion of such operations the operator may, if preferred, simply actuate either the starting switch 20G or the emergency switch 282 so as to open the control circuit and thereby cause all motions to stop and the rolls to open; the control switch 2M and emergency switch 292 being preferably arranged at different positions on the machine to facilitate quick stopping of the machine whenever trouble is noted by the operator. t

However, as illustrated in Fig. 7 an accessory counter switch 203 may be included in the power supply circuit; the actuator lever thereof being Yarranged to be reciprocated responsive to each reciprocative movement of any portion of the machine, such as for example the movement of the main carriage. Thus, the switch 253 may be of any suitable cumulative counter type such as is presently available on the market and preset so that subsequent to a preselected number of oscillations of the Work carriage the switch 263 will operate to open the electrical control circuit, thereby deenergizing the solenoid 2&8 and stopping the entire machine operation. The addition of such a feature to the machine provides an automatic cycle control effect, and would of course eliminate the need of operator-attention to the extent of each batch-treating operation. Thus, a single operator may, for example, attend to the loading and unloading of a series of such machines, and need only start up each machine after he reloads it whereupon the latter willstop itself after a predetermined amount of Work has been performed upon the work pieces.

It is a particular feature of the present invention that there is included in the machine an improved mechanism for adjustably controlling both the Zone of transverseoscillation of the work piece carriage relative to the rolls and the amplitude thereof. The mechanism for accomplishing this is illustrated in Figs. l, 2, 5, 6 to include a pair of bearing blocks 25E-250 which are slidably mounted upon the transverse rail for free sliding movements therealong and interconnected by means of a screwthreaded control rod 252 which is oppositely threaded (that is, right hand and left hand) in the zones of screwthreaded connection thereof with the oppositely disposed bearing blocks Z50-450. The rod 252 carries a manual control wheel 254, whereby-'it will be appreciated that rotation of the wheel 254 will cause the bearing blocks 250-250 tovmove either toward or away from each other. Blocks E50- 25B carry as integral parts thereof nger devices 25E- 255 which are arranged to engage the actuating lever arm 256 of the pilot valve 236 upon transverse reciprocation of the work piece carriage. Thus, it will be appreciated that manual manipulation of the hand wheel 254 will adjust the amplitude of the transverse stroke of the work piece carriage.

The rod 252 also carries a collar 25S which positions thereon a bracket 259 which is engaged through means of a screwthread connection with a second control rod 260 having its head end portion extending to a position within convenient reach of the operator and terminating in a hand 4 wheel 262. The bracket 259 is engaged upon the collar 258 so that the rod 252 is freely rotatable therein; and thus it will be appreciated that manual adjustments of the hand wheel 252 will result in positive displacements of the control rod 252 in directions parallel to the axes of the rolls llt-I6. Thus, the position of the zone of transverse carriage movement relative to the rolls may be laterally shifted at will, independently of adjustments of the amplitude or length of strokes thereof. This feature of the invention facilitates adaptation of the machine to different work piece mountings and to glazing or polishing of variously shaped work pieces, and permits adjustment of the machine to compensate for variable wear of the roll devices and to suit the machine to operate upon widely diierent articles.

It is another feature of the, present invention that a novel operation dwell control arrangement is provided to facilitate any desired slowing down or speeding up of any phase of a reciprocating cycle of the work pieces relative to the rolls I4, I6, whereby the glazing or polishing operation may be emphasized or minimized on different portions of the work pieces, such as may be particularly desirable on work pieces of irregular shapes such as spoons, forks, or the like. For this purpose, by way of one example thereof, Figs. 1-2 and 4 illustrate connection to one end of the shaft 92 of a cam 210 whichis arranged to track against a rollered finger portion 272 ci a throttle valve device 274 which is connected into one of the hydraulic lines leading to the cylinder li controlling oscillation of the work carrying platform (Fig. 9)'. The valve 2N may be oi any suitable type for variably throttling the flow of hydraulic fluid therethrough as controlled by the finger 272, and preferably is provided with a manual" adjustment device 215 whereby the operator may adjust the range of iiuid flow through the valve independently of operation` thereof as provided by the control finger 272. .v y

As shown in Fig. 4, the cam 2l@ isshaped so that as the shaft 92 rocks incidental to operations of the cylinder IDD as explained hereinabove, the cam 210 is thereby caused to variably press against the valve stem 212 so as to provide the desired degree of slowing down `of the rocking movement of the platform i i8 at the desired t phase of its cycle of rocking. Thus,'the device aslaoo is readily adjustable to either emphasize or minimize the amount of glazing or polishing action applied to different areas of thework piecesicarried by the frame I i8. 1

Thus, it will be appreciated that the machine of the present invention embodies novel and irnport-ant operational control and adjustment features which adapt the machine to more nearly fully automatic and otherwise improved modes of operation, especially when' operating upon work pieces of irregular shapes. Also, it will of course be appreciated that although only one form of the machine of the invention has been illustrated and described in detail herein, it will be apparent to those skilled in the art that the invention is not so limited but that various changes may be made therein without departing from the spirit of the invention or the scope of the appended claims. i. i Y

What is claimed is:

l. In a polishing and glazing machine, in combination, a pair of rolls, a slide member movable towards and away from the rolls ina line at right angles to the longitudinal axes of the rolls, a platform carried by said slide member and movable thereon in directions parallel to said rolls, a Work holder carried by said platform by means of pivotal connections therewith having pivot axes parallel to said rolls, means for causingy said slide member and said platform to independently oscillate, and drive means to cause the work holder to pivot relative to saidl platform, said workholder being constructed and arranged so as to support a plurality of work pieces to extend forwardly therefrom for passage between said rolls for polishing or glazing purposes, power supply means coupled to said slide member and to said platform and to said work holder for oscillaw tion thereof, and said drive means being controlled by a variably controllable powerthrottling device in turn controlled by movement of said work holder to vary the speed of pivoting of said holder at different phases of its movements about said pivotal connections thereof.

2. In a polishing and glazing machine, a pair of rolls, a platform carried by said machine and oscillatable thereon, a work holder carried by said platform for oscillation relative thereto, said work holder being constructed and arranged so as to support a plurality of work pieces to extend forwardly therefrom for passage between said rolls for polishing or glazing purposes, hydraulic actuating means including a hydraulic fluid pressure supply and conduit means operable to oscillate said work holder relative to said rolls, a

throttle valve controlling the rate of fluid ow through said conduit means, and cam means geared to said work holder for movement therewith and operable to control said throttle valve for varying the rate of said work holder move ment during different phases .of oscillation thereof.

3. In a polishing and glazing machine for surface nishing batches of work pieces, a pair of parallel rolls,a work holder adapted to mount a plurality of work pieces to be extended toward the gap between said rolls, said holder being carried by said machine by means of connections therewith whereby said workholder is displaceable to reciprocate the work pieces in the polishing gap between the rolls,.hydraulic jack means operable to move said work holder relative to said rolls, and a hydraulic jack controlmeans including a pressured fluid supply conduit system ccntrolled by a reversing direction pilot valve actuated bysaid Worlr holder upon movements thereof in opposite directions, said work holder having positionally adjustable paired abutment devices thereon operable to contact and actuate said pilot valve to thereby determine the limits of the reciprocation strokes of said work holder, and manual control means carried by said holder and operable to selectively shift the positions of said abutment devices relative to said work holder for variations of the rangeof stroke of said holder and the position of said stroke range relative to said rolls.

4. In a polishing and glazing machine, in combination, a roll, a slide member movable towards and away from said roll in a line at right angles to the longitudinal axes of said roll, a platform carried by said slide member and movable thereon in directions parallel to said roll, a work holder carried by said platform by means of .pivotal connections therewith having pivot axes parallel to said roll, means for causing said slide member and said platform to independently cscillate, and hydraulic jack maens to cause the work holder to pivot relative to said platform, said work holder being constructed and arranged so as to support a plurality of work pieces to extend forwardly therefrom for passage against said roll for polishing or glazing purposes, power supply means coupled to said slide member and to said platform and to said work holder for oscillation thereof, said hydraulic jack means being controlled by a throttle valve in turn controlled by movement of said work holder to vary the speed of pivoting of said holder at different phases of its movements about said pivotal connections thereof, and counter means actuated upon movement of said work holder to count the oscillations thereof and operable upon accumulation of a predetermined number of oscillation counts to disconnect said power supply means to stop said machine.

5. In a polishing and glazing machine, in ccmbination, a pair of rolls, roll control means to open and close said rolls relative to one another, a slide member movable towards and away from the rolls in a line at right angles to the longitudinal axes of the rolls, a platform carried by said slide member and movable thereon in directions parallel to said rolls, a work holder carried by said platform by means of pivotal connections therewith having'pivot axes parallel to said rolls, means for causing said slide member and said platform to independently oscillate, and means to cause the work` holder to pivot relative to said platform, said work holder being constructed and arranged so as to support a plurality of wcrl; pieces to extend forwardly therefrom for passage between said rolls for polishing cr glazing pur-- poses, power supply means coupled to said roll control means and to said slide member and to said platform and to said work holder for oscillation thereof, speed control means including speed pattern means responsive to movement of said work holder and adapted to establish a definite correlation between the position of said work holder in its pivotal cycle of oscillation and the speed of pivoting of said work holder according to an arbitrary predetermined pattern, whereby said pivoting may be automatically retarded at any desired predetermined portion of said cycle of oscillation, and counter means actuated upon movement of said Work holder tc count the oscillations thereof and operable upon accumulation of a predetermined number of oscillation counts means geared to said work holder for movement therewith and operable to control said throttle valve for varying the rate of said work holder movement during different phases of oscillation thereof.

7. In a polishing and glazing machine for surface finishing batches of work pieces, a roll, a work holder adapted to mount a plurality of work pieces to be extended toward said roll, said holder being carried by said machine by means of connections therewith whereby said work holder is displaceable to reciprocate the Work pieces against the roll, hydraulic jack means operable to move said work holder relative to said roll, and a hydraulic jack control means including a pressured fluid supply conduit system controlled by a reversing direction pilot valve actuated by said work holder upon movements thereof in opposite directions, said work holder having positionally adjustable paired abutment devices thereon operable to contact and actuate said pilot valve to thereby determine the limits of the reoiprocation strokes of said work holder, and inanual control means carried by said holder and perable to selectively shift the positions of said abutment devices relative to said work holder for variations of the range of stroke of said holder and the position of said stroke range relative to said roll.

8. In a polishing and glazing machine, incomblnation, a pair of rolls, roll control means to open and close said rolls relative to one another, a slide member movable towards and away from the rolls in a line at right angles to the longitudinal axes of the rolls, a hydraulic actuator including fluid pressure supply and conduit means operable to oscillate said slide member relative to said rolls, a throttle valve controlling the rate of fluid ow through said conduit means, and cam means geared to said slide member for move- 10 ment therewith and operable to control said throttle Valve for varying the rate of said slide member movement during different phases of oscillation thereof, a platform carried by said slide member and movable thereon in directions parallel to said rolls, hydraulic jack means operable to move said platform relative to said rolls, and a hydraulic jack control means including a pressured uid supply conduit system controlled by a reversing direction pilot valve actuated by said platform upon movements thereof in opposite directions, said platform having positionally adjustable paired abutment devices thereon operable to contact and actuate said pilot valve to thereby determine the limits of the reciprocation strokes of said platform, and manual control means carried by said platform and operable to selectively shift the positions of said abutment devices relative to said platform for variations of the range of stroke of said platform and the position of said stroke range relative to said rolls, a work holder carried by said platform by means of pivotal connections therewith having pivot axes parallel to said rolls, means for causing said slide member and said platform to independently oscillate, and means to cause the work holder to pivot relative to said platform, said work holder being constructed and arranged so as to support a plurality of work pieces to extend forwardly therefrom for passage between said rolls for polishing or glazing purposes, power supply means coupled to said roll control means and to said slide member and to said platform and to said work holder for oscillation thereof, and counter means actuated upon movement of said work holder to count the oscillations thereof and operable upon accumulation of a predetermined number of oscillation counts to disconnect said power supply means to stop said machine and to open said rolls.

WILLIAM C. BURT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 557,825 Johnston Apr. 7, 1896 2,079,785 Ackley May 11, 1937 2,425,234 Erwin et al Aug. 5, 1947 2,458,708 Johnson et al Jan. 11, 1949 

